- ID:
- ivo://CDS.VizieR/J/ApJS/109/489
- Title:
- OH observations of Arecibo OH/IR stars
- Short Name:
- J/ApJS/109/489
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Arecibo 1612MHz survey of a complete sample of color-selected IRAS sources with 25{mu}m fluxes S(25)>2 Jy detected 393 OH/IR stars. A complementary 1667 and 1665MHz OH survey of these objects is presented here. Main-line masers have been detected in 238 surveyed objects: 18 exhibit only 1665MHz emission, 220 exhibit 1667MHz masers, and 119 exhibit both. The main lines were not detected in 159 objects.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/123/2772
- Title:
- OH-selected AGB and post-AGB objects. I.
- Short Name:
- J/AJ/123/2772
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 766 compact objects found in a systematic survey of the Galactic plane in the 1612MHz masing OH line, new light is cast on the IR properties of evolved stars on the thermally pulsing asymptotic giant branch (AGB) and beyond. The usual mid-IR selection criteria for post-AGB, based on IRAS colors, largely fail to distinguish early post-AGB stages. A two-color diagram from much narrower band MSX flux densities, with bimodal distributions, provides a better tool for doing this. Four mutually consistent selection criteria for OH-masing red protoplanetary nebulae are given, as well as two for early post-AGB masers and one for all post-AGB masers including the earliest ones. All these criteria miss a group of blue, high-outflow post-AGB sources with 60{mu}m excess; these will be discussed in detail in Paper II (Sevenster, 2002AJ....123.2772S). The majority of post-AGB sources show regular double-peaked spectra in the OH 1612MHz line, with fairly low outflow velocities, although the fractions of single peaks and irregular spectra may vary with age and mass. The OH flux density shows a fairly regular relation with the stellar flux and the envelope optical depth, with the maser efficiency increasing with IRAS color R_21_. The OH flux density is linearly correlated with the 60{mu}m flux density.
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/220
- Title:
- Optical redshifts of OH- and HI-emitting galaxies
- Short Name:
- J/MNRAS/459/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- OH megamasers (OHMs) are rare, luminous molecular masers that are typically observed in (ultra) luminous infrared galaxies and serve as markers of major galaxy mergers. In blind emission line surveys such as the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) survey for neutral hydrogen (HI), OHMs at z~0.2 can mimic z~0.05 HI lines. We present the results of optical spectroscopy of ambiguous HI detections in the ALFALFA 40 per cent data release detected by the Wide Field Infrared Survey Explorer (WISE) but with uncertain optical counterparts. The optical redshifts, obtained from observations at the Apache Point Observatory, revealed five new OHMs and identified 129 HI optical counterparts. 60 candidates remain ambiguous. The new OHMs are the first detected in a blind spectral line survey. The number of OHMs in ALFALFA is consistent with predictions from the OH luminosity function. Additionally, the mid-infrared magnitudes and colours of the OHM host galaxies found in a blind survey do not seem to differ from those found in previous targeted surveys. This validates the methods used in previous IR-selected OHM surveys and indicates there is no previously unknown OHM-producing population at z~0.2. We also provide a method for future surveys to separate OH megamasers from 99 per cent of HI line emitters without optical spectroscopy by using WISE infrared colours and magnitudes. Since the fraction of OHMs found in flux-limited HI surveys is expected to increase with the survey's redshift, this selection method can be applied to future flux-limited high-redshift hydrogen surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A126
- Title:
- Orion Source I 3mm SiO maser emission
- Short Name:
- J/A+A/606/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-mass star formation remains poorly understood due to observational difficulties (e.g. high dust extinction and large distances) hindering the resolution of disk-accretion and out ow-launching regions. Orion Source I is the closest known massive young stellar object (YSO) and exceptionally powers vibrationally excited SiO masers at radii within 100AU, providing a unique probe of gas dynamics and energetics. We seek to observe and image these masers with Very Long Baseline Interferometry (VLBI). We present the first images of the ^28^SiO v=1, J=2-1 maser emission around Orion Source I observed at ({lambda}2mm) with the Very Long Baseline Array (VLBA). These images have high spatial (~0.3mas) and spectral (~0.054km/s) resolutions.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/130
- Title:
- Parallaxes of high mass star forming regions
- Short Name:
- J/ApJ/783/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Over 100 trigonometric parallaxes and proper motions for masers associated with young, high-mass stars have been measured with the Bar and Spiral Structure Legacy Survey, a Very Long Baseline Array key science project, the European VLBI Network, and the Japanese VLBI Exploration of Radio Astrometry project. These measurements provide strong evidence for the existence of spiral arms in the Milky Way, accurately locating many arm segments and yielding spiral pitch angles ranging from about 7{deg} to 20{deg}. The widths of spiral arms increase with distance from the Galactic center. Fitting axially symmetric models of the Milky Way with the three-dimensional position and velocity information and conservative priors for the solar and average source peculiar motions, we estimate the distance to the Galactic center, R_0_, to be 8.34+/-0.16kpc, a circular rotation speed at the Sun, {Theta}_0_, to be 240+/-8km/s, and a rotation curve that is nearly flat (i.e., a slope of -0.2+/-0.4km/s/kpc) between Galactocentric radii of {approx}5 and 16kpc. Assuming a "universal" spiral galaxy form for the rotation curve, we estimate the thin disk scale length to be 2.44+/-0.16kpc. With this large data set, the parameters R_0_ and {Theta}_0_are no longer highly correlated and are relatively insensitive to different forms of the rotation curve. If one adopts a theoretically motivated prior that high-mass star forming regions are in nearly circular Galactic orbits, we estimate a global solar motion component in the direction of Galactic rotation, V_{sun}_=14.6+/-5.0km/s. While {Theta}_0_and V_{sun}_are significantly correlated, the sum of these parameters is well constrained, {Theta}_0_+V_{sun}_=255.2+/-5.1km/s, as is the angular speed of the Sun in its orbit about the Galactic center, ({Theta}_0_+V_{sun}_)/R_0_=30.57+/-0.43km/s/kpc. These parameters improve the accuracy of estimates of the accelerations of the Sun and the Hulse-Taylor binary pulsar in their Galactic orbits, significantly reducing the uncertainty in tests of gravitational radiation predicted by general relativity.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A74
- Title:
- POETS luminous YSOs 13 or 22GHz images
- Short Name:
- J/A+A/631/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although recent observations and theoretical simulations have pointed out that accretion disks and jets can be essential for the formation of stars with a mass of up to at least 20M_{sun}_, the processes regulating mass accretion and ejection are still uncertain. The goal of the Protostellar Outflows at the EarliesT Stages (POETS) survey is to image the disk-outflow interface on scales of 10-100au in a statistically significant sample (36) of luminous young stellar objects (YSO), targeting both the molecular and ionized components of the outflows. The outflow kinematics is studied at milliarcsecond scales through very long baseline interferometry (VLBI) observations of the 22GHz water masers, which are ideal test particles to measure the three-dimensional (3D) motion of shocks owing to the interaction of winds and jets with ambient gas. We employed the Jansky Very Large Array (JVLA) at 6, 13, and 22GHz in the Aand B-Array configurations to determine the spatial structure and the spectral index of the radio continuum emission, and address its nature. In about half of the targets, the water masers observed at separation <=1000au from the YSOs trace either or both of these kinematic structures: 1) a spatially elongated distribution oriented at close angle with the direction of collimation of the maser proper motions (PM), and 2) a linear local standard of rest (LSR) velocity (VLSR) gradient across the YSO position. The kinematic structure (1) is readily interpreted in terms of a protostellar jet, as confirmed in some targets via the comparison with independent observations of the YSO jets, in thermal (continuum and line) emissions, reported in the literature. The kinematic structure (2) is interpreted in terms of a disk-wind (DW) seen almost edge-on on the basis of several pieces of evidence: first, it is invariably directed perpendicular to the YSO jet; second, it agrees in orientation and polarity with the VLSR gradient in thermal emissions (when reported in the literature) identifying the YSO disk at scales of <=1000au; third, the PMs of the masers delineating the VLSR gradients hint at flow motions at a speed of 10-20km/s directed at large angles with the disk midplane. In the remaining targets, the maser PMs are not collimated but rather tend to align along two almost perpendicular directions. To explain this peculiar PM distribution, and in light of the observational bias strongly favoring masers moving close to the plane of sky, we propose that, in these sources, the maser emission could originate in DW-jet systems slightly inclined (<=30{deg}) with respect to edge-on. Magneto-centrifugally driven DWs could in general account for the observed velocity patterns of water masers.
- ID:
- ivo://CDS.VizieR/J/ApJ/728/149
- Title:
- Polarized SiO masers of VX Sgr
- Short Name:
- J/ApJ/728/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Submillimeter Array observations of high-frequency SiO masers around the supergiant VX Sgr and the semi-regular variable star W Hya. The J=5-4, v=1^28^SiO and v=0^29^SiO masers of VX Sgr are shown to be highly linearly polarized with a polarization from ~5% to 60%. Assuming the continuum emission peaks at the stellar position, the masers are found within ~60mas of the star, corresponding to ~100AU at a distance of 1.57kpc. The linear polarization vectors are consistent with a large-scale magnetic field, with position and inclination angles similar to that of the dipole magnetic field inferred in the H_2_O and OH maser regions at much larger distances from the star. We thus show for the first time that the magnetic field structure in a circumstellar envelope can remain stable from a few stellar radii out to ~1400AU. This provides further evidence supporting the existence of large-scale and dynamically important magnetic fields around evolved stars. Due to a lack of parallactic angle coverage, the linear polarization of masers around W Hya could not be determined. For both stars, we observed the ^28^SiO and ^29^SiO isotopologues and find that they have a markedly different distributions and that they appear to avoid each other. Additionally, emission from the SO 5_5_-4_4_ line was imaged for both sources. Around W Hya, we find a clear offset between the red- and blueshifted SO emission. This indicates that W Hya is likely host to a slow bipolar outflow or a rotating disk-like structure.
- ID:
- ivo://CDS.VizieR/J/other/PASA/26.454
- Title:
- Precise positions of methanol masers
- Short Name:
- J/other/PASA/26.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope Compact Array (ATCA) has been used to determine positions for many southern methanol maser sites, with accuracy better than 1 arcsec. The results are presented here as a catalogue of more than 350 distinct sites, some of them new discoveries, and many others with positional precision 10-times better than existing published values. Clusters of 2 or 3 sites are occasionally found to account for single previously listed sources. This in turn reveals that the velocity range for each individual site is sometimes smaller than that of the originally tabulated (blended) source. Only a handful of examples then remain with a velocity range of more than 16km/s at a single compact (less than 2 arcsec) site. The precise methanol positions now allow apparent coincidences with OH masers to be confidently accepted or rejected; this has led to the important conclusion that, where a 1665-MHz OH maser lies in a massive star formation region, at more than 80 percent of the OH sites there is a precisely coincident methanol maser. The methanol precision achieved here will also allow clear comparisons with likely associated IR sources when the next generation of far-IR surveys produce precise positions.
- ID:
- ivo://CDS.VizieR/J/AJ/144/129
- Title:
- Properties of 83 known stellar SiO maser sources
- Short Name:
- J/AJ/144/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out simultaneous observations of four maser lines, SiO v=1,2, ^29^SiO v=0,J=1-0, and H_2_O 6_16_-5_23_, toward 83 known SiO maser sources without H_2_O maser detections using the Korean VLBI Network single dish telescopes. Both SiO and H_2_O masers were detected from 14 sources, resulting in a detection rate of 16.9%. H_2_O maser emission without SiO maser emission was detected from one source. Therefore, H_2_O maser emission was newly detected from 15 sources. SiO maser emission without H_2_O detection was detected from 55 sources, which gives a total SiO maser detection rate of 83.1% when including sources that have both SiO and H_2_O maser emission detected. SiO v=2 maser emission was detected from nine sources without v=1 maser detection. The SiO v=2 maser sources without the v=1 maser detections need to be investigated, with a large number of v=2 only maser sources related to the development of dust shells and their evolutionary sequence from asymptotic giant branch (AGB) to post-AGB stars. The average values of the peak and integrated antenna temperature ratios of H_2_O to SiO masers are 0.44 and 0.28 in the 14 sources that have both SiO and H_2_O detections. Observational characteristics of several individual sources are noted and the dependence of the different maser intensity ratios on the stellar phase is discussed. In addition, the observational results of SiO and H_2_O masers are discussed in IRAS two-color diagrams.
- ID:
- ivo://CDS.VizieR/J/A+A/368/1006
- Title:
- Properties of OH/IR stars with IRAS LRS spectra
- Short Name:
- J/A+A/368/1006
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This table contains the selected from the literature sample of 1065 OH maser sources with IRAS identification and LRS spectra. The most important physical quantities of these sources are assembled and the list of related references together with the abbreviations used is attached.
